This invention relates to a radioactive rays detection semiconductor device for detecting radioactive rays, particularly to a radioactive rays detection semiconductor device for detecting a vast amount of a total dose of radioactive rays.
In the fields of space industry and the atomic power industry, a radioactive rays detection semiconductor device using a MOS transistor or the like is widely used to detect a vast amount (-10.sup.6 Gy) of a total dose of radioactive rays. The total dose of radioactive rays is detected by detecting the change of the electric characteristics of the detection element when the element receives the radioactive rays.
FIG. 1 shows the structure of the conventional radioactive rays detection semiconductor device having a MOS transistor structure. In this device, two n-type diffusion films 2a and 2b respectively serving as source and drain are formed in a p-type semiconductor substrate 1, as shown in FIG. 1. On a channel region between the two n-type diffusion films 2a and 2b, a gate electrode 4 is formed on a gate electrode insulating layer 3 which is sandwiched by the channel region and the gate electrode. On these elements, an insulating film 7 is deposited and electrodes 5 and 6 are formed to contact with the two diffusion films 2a and 2b.
The electrodes 5 and 6 are applied with a positive voltage and the gate electrode is applied with a negative voltage. By applying the voltages in such a manner, a depletion layer is generated between the two n-type diffusion films 2a and 2b. When radioactive rays are incident on the depletion layer, the ionization occurs in the depletion layer to generate positive and negative charges. The positive and negative charges change a value of an electric current flowing between the electrodes 5 and 6. By detecting the change of the electric current value, the total dose of the radioactive rays incident in the element can be obtained.
In detecting the dose of the radioactive rays with use of the conventional radioactive rays detection semiconductor device having the above-mentioned structure, however, some problems will occur: the output of the detection element, i.e., the electric characteristics of the element will be also changed due to the change of the temperature of the element. Therefore, not only the change due to the radioactive rays but also that due to the temperature change of the element will be detected simultaneously, and thus the total dose of the radioactive rays cannot be detected without the error due to the temperature change.
Accordingly, with use of the conventional radioactive rays detection semiconductor device, the total dose of the radioactive rays cannot be detected with high precision in the environment such as space or atomic power industry facilities in which the ambient temperature or the intensity of the radioactive rays will change as time passes or area is increased/decreased.
The object of the present invention is thus to provide a semiconductor device capable of highly precise detection of the total dose of the radioactive rays without being affected by the temperature change in the environment in which the radioactive rays are detected or by the heat generated by the change of the intensity of the radioactive rays.